The Best Plants for Retaining Walls

Retaining walls present unique challenges to the gardener. This is how you overcome them.

Dull retaining walls

The pre-cast, interlocking cement retaining block, with its handy hole for planting in, is without doubt one of the best solutions to tame a slope and prevent soil erosion. But unplanted retaining walls built with these blocks are not necessarily a joy to the eye!

To establish a vertical garden in a retaining wall, which normally dry out fast and can only hold plants with shallow or small root systems, needs some homework before buying the right plants.

Handle retaining walls the following way:

• Tell the building contractor before the wall is erected that you’re planning on planting up the hollows and that you want them filled with top-quality topsoil, and not the bad sub-soil they normally use.

• Order a bulk load of compost and mix one part of compost to two parts of topsoil.

• If you can, add bonemeal to this mix, or spread it over the soil if the hollows have already been filled.

• It’s also a good idea to work in some water-retention granules before planting. This will keep the soil moist in warm weather and help to establish the plants faster.

Water works for retaining walls

Even if you don’t have an automatic irrigation system in the rest of your garden, it’s recommended that you install a micro-irrigation system along the wall – even if it’s just a simple DIY system with small pipes and light sprinklers that can be coupled to a tap to be operated manually.

More tips

• Rather plant young perennials bought in trays than plants in 4-litre nursery bags or pots – it’s difficult to make big planting holes in the blocks.

• If you pick spreading and cascading groundcovers you don’t have to fill every hole, and can even skip a row by planting them in a zigzag pattern. Start at the top of the wall and work your way down.

• Regular cutting back, watering and feeding in spring and autumn will keep the plants we recommend below healthy and lush, even though they are naturally hardy and waterwise.

• To create a colourful wall, use more than one type of plant by all means, but plant in bold groups rather than dotting them in a mixed fruit-salad manner – a mass is always more impressive.

The right plants

Aptenia cordifolia (brakvygie)

Cascading,  fleshy leaves and small rose-pink vygie  flowers in spring. Good for full sun, it is hardy and drought hardy.

Lampranthus spp. (vygie)

A succulent with luminescent  owers in many colours in spring. Spreading and fast growing, it enjoys full sun and is drought hardy.

Carpobrotus edulis (sour fig)

Thick  fleshy leaves and large yellow  flowers that mature to dull pink. It is good for full sun and is very drought hardy.

Gazania rigens (trailing gazania)

Silvery to deep green leaves and dark yellow  flowers. Spreading and fast growing, it is good for full sun and is drought hardy.

Helichrysum cymosum subsp. cymosum (gold carpet)

Silvery small leaves and a mass of bright yellow flowers in late summer and autumn. Good for full sun and very well-draining soil. Hardy and drought resistant.

Asystasia gangetica (creeping foxglove)

Dark green leaves and aromatic creamy  flowers in summer. A fast grower for light shade that likes rich soil and regular watering.

Dimorphotheca jucunda (osteospermum)

Large daisy  flowers in white, pink and purple from autumn to spring. Spreading and fast growing in full sun with regular watering.

Pelargonium peltatum (ivy-leaf geranium)

Bright  flower colours in every shade all year long. Spreading and fast growing in full sun with regular watering and feeding.

Coleus neochilus (spur flower)

Previously known as Plectranthus neochilus. It has hairy leaves and bright blue flowers from late winter to autumn. Drought resistant, and does well in full sun and light shade.

Crassula multicava (fairy crassula)

A fast-growing, low maintenance and drought-resistant groundcover that thrives in sun or shade. It flowers generously from May to September.